Swamped

Part of the reason it takes you a while is that this isn't even a sea chart. It's a map of the damned desert. It's just that so much of it is empty that it looks like ocean.

Which makes the island all the stranger. And what are the shoals around it if this is all land? Why do you even have a map of the desert, it's not like you can sail there...

Wait... no, hold on, now you remember. This is a map of weather patterns. It's mainly a reference so you know the symbols when you have to put down weather notes on your own maps... which, come to think of it, is something you ought to get around to. The "shoals" are actually strong winds.

Thing is, you only know what it is because you had a quick talk with the retiring navigator before taking over. Most of these maps are his, barring a few you bought before the ship left. He didn't mention anything about how he came by them.

Could he have made this map himself? But then why would he leave it on the ship, and risk this secret being discovered? You wouldn't have thought anything of it if he'd taken this particular map with him.

Suppose he did, though. Maybe he was confident enough that the paper would hold for the entire voyage. Then how would it get loose?

Maybe by someone poking at it. But that would be even stranger. Whoever it was would have to know about the map... and yet, aside from the Captain and two of the other officers, this is supposed to be an entirely new crew. So who would even know this map was here?

You're left with a lot of questions. At the same time, is it really your job to answer them? Your head still hurts a bit, and you've got maps that need taking care of. You still need to figure out what to do about the crow's nest issue, too...

You get over to the bed and lie down. No sense stressing yourself too much. Yeah, there's work to be done, but it should be fine to hold off on it for a day or so while you recover...

...Oh. Except for that matter you just remembered.